Document ESP binary blobs

[antoniovazquezblanco]

It would be useful for reversing efforts to document ESP binary blobs locations, functionality and dependencies.

Some examples of blobs:
https://github.com/espressif/esp-rom-elfs
https://github.com/espressif/esp-phy-lib

Dependency information can be found in ESP IDF CMake files:
https://github.com/espressif/esp-idf/blob/636ff35b52f10e1a804a3760a5bd94e68f4b1b71/components/esp_phy/CMakeLists.txt#L77